Wells are generally drilled into a land surface or ocean bed to recover natural deposits of oil and gas, as well as other natural resources that are trapped in geological formations in the Earth's crust. Wellbores may be drilled along a trajectory to reach one or more subterranean rock formations containing the hydrocarbons and other downhole fluids. Formation evaluation and other downhole tools and operations have become increasingly complex and expensive as wellbores are drilled deeper and through more difficult materials. Such wellbores present increasingly harsher environments, where temperature may exceed 250 degrees Celsius and pressure may exceed 30,000 pounds per square inch (PSI).
In working with deeper and more complex wellbores, it becomes more likely that downhole tools, tool strings, and/or other downhole apparatuses may include numerous testing, navigation, and/or communication tools. Extreme downhole conditions may subject such tools to a variety of loads, including but not limited to pressure differential, tension, compression, hydraulic force, shock, and vibrations. Such loads can damage the tools, cause downhole fluids to leak into the tools, and/or otherwise compromise the accuracy and even operation of the tools.
To minimize effects of the extreme downhole conditions, various empty cavities or chambers within downhole tools may be pressure compensated and, thus, filled with a fluid operable to maintain internal portions of the downhole tools at a pressure substantially equal to the wellbore pressure. Gas, such as air, trapped within the downhole tools may prevent or reduce the benefits of pressure compensation and/or cause damage or unintended operation of the downhole tools while being subjected to the high pressure and/or high temperature wellbore environments. Accordingly, gas is typically purged or extracted from the various cavities and chambers of the downhole tools prior to or during fluid filling operations. However, fluid filling operations, such as gravity filling, vacuum filling, and gas flushing are typically unable to completely purge or extract gas from the cavities and chambers, especially cavities and chambers having arbitrary and/or complex geometries, which may act to trap gas therein. Such filling operations often leave a variable and not easily determined amount of residual gas within the cavities and chambers. To overcome the unintended effects of residual gas, the downhole tools may be increased in length and thickness. However, in downhole oil and gas operations, where space is valuable, an increase in size and weight has the effect of decreasing operational efficiency and increasing cost.